This invention relates to a ring binder mechanism of the type wherein opposed half-rings are carried on a pair of elongate blades retained in edge-to-edge relationship in a spring housing. In such a mechanism the blades carrying the half-rings are movable with a toggle action against the resilience of the spring housing between an open position, in which opposed half-rings are separated, and a closed position in which the ends of opposed half-rings abut against one another.
In such mechanisms it is known to provide a locking device engaging the blades and being operable to restrain the half-rings against opening movement from their closed position. Such a locking device may also be operable to function as a "booster" to facilitate movement of the half-rings between their open and closed positions and vice versa. Ring binder mechanisms of this type are described and illustrated in U.S. Pat. No. 1,787,957 and U.S. Pat. No. 2,030,473 wherein the locking device comprises a trigger carried on the housing and having means thereon to engage the blades. In U.S. Pat. No. 1,787,957 the trigger is pivotally mounted on the housing by means of a pivot pin whilst in U.S. Pat. No. 2,030,473 the trigger has a pivoting and sliding movement relative to the blades by means of a bifurcated pin engaging the blades.
Mechanisms constructed as aforesaid are relatively complex and therefore expensive to produce and it is an object of the present invention to provide a locking ring binder mechanism which overcomes certain at least of these disadvantages.